update VLLM_ENABLE_OUTPUT_PLACEHOLDERS

vllm/v1/core/sched/scheduler.py

@@ -76,7 +76,7 @@ class Scheduler(SchedulerInterface):
             self.kv_events_config is not None
             and self.kv_events_config.enable_kv_cache_events)
         # Cache the output placeholders feature flag to avoid repeated envs access
-        self.enable_output_placeholders = envs.is_set("VLLM_ENABLE_OUTPUT_PLACEHOLDERS")
+        self.enable_output_placeholders = envs.VLLM_ENABLE_OUTPUT_PLACEHOLDERS
 
         # Create KVConnector for the Scheduler. Note that each Worker
         # will have a corresponding KVConnector with Role=WORKER.